The present invention is related to the field of vehicle data recorders.
High speed microprocessors, electronic fuel injectors, sensors, and actuators allow the operation of modern internal combustion engines and transmissions to be placed under software control. The sensors provide the software with all of the necessary data items required to understand the engine and transmission dynamics, and the electronic fuel injectors and actuators provide a means for implementing control of the various engine and transmission functions. Coupling the microprocessor to a non-volatile memory of a vehicle data recorder permits the software to store various historical data items for later analysis. These data items are often related to the power train, typically the engine and transmission, as well as other vehicle parameters. Data items stored in the memory can be retrieved through reports generated by software executing in the microprocessor or another external computer. Operators and owners of the vehicle can determine from these reports how well the vehicle or operator has been performing as well as various details about trips taken by the vehicle.
The ability of the software to gather and store data items often exceeds the capacity of the non-volatile memory to record that data. Consequently, the user must decide which data items are important and should be recorded in non-volatile memory, and which data items are to be stored in volatile memory. This decision may change from time to time and from user to user. It is therefore desirable to be able to dynamically select which data items are recorded in non-volatile memory.
Data items are often grouped together into pages that are stored in the non-volatile memory. Each page typically contains data items that have some common nexus. For example, all the diagnostics information may be contained on one page while all the engine usage data is contained on a second page. This can lead to confusion and problems as individual data items and individual pages are enabled and disabled for recording data items. A common design practice is to leave historical data items in their respective pages even though recording for that page has been disabled. This leads to the various pages and individual data items being out of sync with each other as a function of time. For example, an enabled diagnostics page may record an engine coolant reaching a high temperature threshold while a disabled engine usage page contains old data showing the engine operating at low idle. Here, maintenance personnel could be easily confused by a report containing simultaneously both the current high coolant temperature diagnostic data and the obsolete low engine idle data.
The present invention is a method of operating an electronic control module, and an information recording medium recording a computer program executable by the electronic control module, for erasing historic data items when subsequent recording of individual data items or a page of data items has been disabled. Erasing historical data items avoids any confusion that may result from having a mix of obsolete and current data items recorded. Historical data items to be erased fall into at least two categories, event items and accumulation items. Event items that are based on random events such as a variable crossing of a threshold, or a periodic event such as a value at each tick of a clock. Accumulation items generally produce values that tend to move in one direction only, such as a trip odometer.
In operation, the method of the present invention involves disabling recording of the one or more event items associated with a selected page in memory for which recording is to be stopped. Next, all of the event items and all of the accumulation items for that selected page are erased. Accumulator items reflected in the selected page may be allowed to continue to be stored after the selected page has been disabled and erased. As a result, accumulator items on the selected page are erased again when recording in the selected page is reenabled. This is done to maintain synchronization among the event items and the accumulator items recorded in the selected page. Once recording in the selected page has been reenabled, recording of all event items associated with that page are reenabled.
In an alternative embodiment, recording of accumulator items may be suspended in the selected page while the historical data items are being erased. Disabling recording of accumulator items, erasing historical accumulator items, and then reenabling recording of accumulator items prevents updates of accumulator items while the selected page is being erased. This helps maintain synchronization among the individual accumulator items within the selected page.
In another alternative embodiment, recording of accumulator items may be suspended in the selected page and remain suspended after the historical data has been erased. This embodiment maintains synchronization between the accumulator items and event items so that both are disabled, erased, and enabled together.
In yet another alternative embodiment, enablement and disablement for recording data items may be performed at the individual data item level. Here, when one even item of a page is disabled, then all event items of that page are disabled while the historical data items are erased. Recording of all event items, except for the selected event item disabled, is reenabled after erasure is completed. When recording of the selected event item is reenabled then recording of all event items is disabled, the historical data items are erased, and then recording of all event items is reenabled. The same method is be applied to individual accumulator items where recording of all accumulator items is disabled before erasure, and then reenabled after erasure.
Accordingly, it is an object of the present invention to provide a method, and an information recording medium recording a computer program implementing the method, for erasing historical data items in a selected page of a memory when recording for one or more data items in that page have been disabled.
These and other objects, features and advantages will be readily apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.